1. Field of the Invention
The present invention relates to an electrochromic display device.
2. Description of Related Art
The publications in the forms of electronic books, that is, electronic publishing, have come to be actively performed in place of the publications by conventional printing techniques as electronic information networks have spread. As the apparatus displaying electronic information to be distributed in these networks, for example, cathode ray tube (CRT) displays and back light type liquid crystal displays have been used. However, the displays by means of these displays are restricted in places to be read, and are inferior also in the handling aspects of the displays in terms of their weights, sizes, shapes, and portability in comparison with the common displays printed on paper. Moreover, because these displays consume much electric power, the restriction of display times is also caused in the case of battery drives. Furthermore, all of these displays is a light emitting type display, and has the problem of causing extreme fatigue at the time of a long hour steady gaze.
Consequently, a display device capable of settling the problems mentioned above is desired, and further a rewritable display device is desired. As these display devices, a display called a paper-like display or electronic paper has been proposed. To put it concretely, for example, the following display devices have been proposed in the past: the display device of a reflective liquid crystal system, the display device of an electrophoretic system, the display device of the system of rotating dichromatic particles in an electric field, and the display device of an electrochromic system (see, for example, Japanese Patent Application Laid-Open Publication Nos. 2003-270671 and 2008-032911).
Incidentally, a display device of the electrochromic system (electrochromic display device) performs the display of an image and the erasion of the displayed image in the manner as shown in FIG. 11, for example. That is, the display of image is performed by an energization to color the pixels which are selected (selection pixels), in which a negative voltage is applied to a line electrode (a first electrode) to form selection pixels, and a positive voltage is applied to a data electrode (a second electrode) to form the selection pixels. Further, the erasion of the displayed image is performed by an energization which is in the reverse direction of the energization performed to color the selection pixels, in which the positive voltage is applied to the first electrode, and the negative voltage is applied to the second electrode.
However, an electrolyte solution is filled in between the electrodes. Thereby, when the energization to color the selection pixels is performed, the electrodes to form the selection pixels are polarized, so as to bring about a state of such as an electrolyte capacitor, a battery cell, or the like. That is to say, after the energization to color the selection pixels is performed, an electric charge remains in between the electrodes which form the selection pixels. Such electric charge moves out to the surroundings through the electrolyte solution, to reach in between the electrodes which form the non-selection pixels. Accordingly, for example, when a high-speed scanning is performed to display a given image repeatedly, the next energization happens to be performed before the remaining electric charge has been eliminated. Thus, the electric charge is to be accumulated in between the electrodes which form the non-selection pixels, and the non-selection pixels happen to be colored. Thereby, there has been a problem that a blurred image happens to be displayed, in which the selection pixels appear to be smudged. Accordingly, it may be conceived that a partition wall be formed in between the pixels in order to prevent the remaining electric charge from moving so that the pixels are separated. However, forming such partition walls requires accuracy and meticulousness for positioning, and the like, thus results in a great deal of burden.
Further, when the high-speed scanning is performed, and the displayed image is erased before the remaining electric charge is eliminated, there also is a problem that the erasion takes much time due to the influence from the remaining electric charge.